Integral locates origin of high-energy emission from Crab Nebula

August 29, 2008
This image shows the direction of polarisation (alignement) of the high-energy radiation emitted by the Crab Nebula, as detected by ESA’s Integral gamma-ray observatory. The shaded part represents the error in the determination of this direction. This direction is remarkably aligned with the inner jets of the Crab. On their turn, these are aligned with the rotation axis of the pulsar located at the centre of the system. The Crab Nebula image in the background was obtained by combining an optical image by NASA/ESA’s Hubble Space Telescope and an X-ray image by NASA’s Chandra X-ray observatory. Credits: NASA/CXC/ASU/J. Hester et al.(for the Chandra image); NASA/HST/ASU/J. Hester et al. (for the Hubble image)

(PhysOrg.com) -- Thanks to data from ESA's Integral gamma-ray observatory, scientists have been able to locate where particles in the vicinity of the rotating neutron-star in the Crab Nebula are accelerated to immense energies.

The discovery, resulting from more than 600 individual observations of the nebula, put in place another piece of the puzzle in understanding how neutron stars work.
Rotating neutron-stars, or pulsars, are known to accelerate particles to enormous energies, typically one hundred times more than the most powerful accelerators on Earth, but scientists are still uncertain exactly how these systems work and where the particles are accelerated.

A step forward in this understanding is now accomplished thanks to a team of researchers from the UK and Italy, led by Professor Tony Dean of the University of Southampton, who studied high-energy polarised light emitted by the Crab Nebula – one of the most dramatic sights in deep space.

The Crab Nebula is the result of a supernova explosion which was seen from Earth on 4 July 1054. The explosion left behind a pulsar with a nebula of radiating particles around it. The pulsar contains the mass of the Sun squeezed into a volume of about 10 km radius, rotating very fast – about 30 times a second – thereby generating very powerful magnetic fields and accelerating particles. A highly collimated jet, aligned with the spin axis of the pulsar and a bright radiating ‘donut’ structure (or torus) around the pulsar itself, are also seen.

So, the Crab is known to accelerate electrons - and possibly other particles - to extremely high speed, and so produces high energy radiation. But where exactly are these particles accelerated?

Looking into the heart of the pulsar with Integral’s spectrometer (SPI), the researchers made a detailed study to assess the polarization – or the alignment - of the waves of high-energy radiation originating from the Crab.

They saw that this polarised radiation is highly aligned with the rotation axis of the pulsar. So they concluded that a significant portion of the electrons generating the high-energy radiation must originate from a highly-organised structure located very close to the pulsar, very likely directly from the jets themselves. The discovery allows the researchers to discard other theories that locate the origin of this radiation further away from the pulsar.

Professor Tony Dean of the University’s School of Physics and Astronomy commented that the discovery of such alignment – also matching with the polarisation observed in the visible band - is truly remarkable. “The findings have clear implications on many aspects of high energy accelerators such as the Crab,” he added.

"The detection of polarised radiation in space is very complicated and rare, as it requires dedicated instrumentation and an in-depth analysis of very complex data”, said Chris Winkler, Integral Project Scientist at ESA. “Integral’s ability to detect polarised gamma-radiation and, as a consequence, to obtain important results like this one, confirms it once more as a world-class observatory.”

Click here to listen to the audio file from Crab.

The results are published in the 29 August issue of the scientific journal Science, in a paper titled ‘Polarized gamma-ray emission from the Crab’, by: A. J. Dean, D.J. Clark, V.A.McBride, A.J.Bird, A.B.Hill and S.E.Shaw (University of Southampton’s School of Physics and Astronomy); J.B. Stephen and L. Bassani (INAF-IASF, Bologna); and A. Bazzano and P. Ubertini (INAF-IASF, Roma).

Provided by ESA

Explore further: Scientific balloon set to measure gamma rays from the Crab Pulsar

Related Stories

First H.E.S.S. II data reveal promising pulsar signal

July 8, 2014

Following the intensive commissioning phase of the largest Cherenkov telescope worldwide (H.E.S.S. CT5), the H.E.S.S. collaboration has announced the detection of cosmic gamma rays of 30 gigaelectronvolts (GeV). The High ...

NASA Goddard astrophysicist wins prize for pulsar work

February 4, 2013

To say that Alice Harding, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Md., has a passion for pulsars is a bit of an understatement. On Jan. 24, she was named a winner of the 2013 Bruno Rossi prize ...

Recommended for you

Distant planet's interior chemistry may differ from our own

September 1, 2015

As astronomers continue finding new rocky planets around distant stars, high-pressure physicists are considering what the interiors of those planets might be like and how their chemistry could differ from that found on Earth. ...

New Horizons team selects potential Kuiper Belt flyby target

August 29, 2015

NASA has selected the potential next destination for the New Horizons mission to visit after its historic July 14 flyby of the Pluto system. The destination is a small Kuiper Belt object (KBO) known as 2014 MU69 that orbits ...

Image: Hubble sees a youthful cluster

August 31, 2015

Shown here in a new image taken with the Advanced Camera for Surveys (ACS) on board the NASA/ESA Hubble Space Telescope is the globular cluster NGC 1783. This is one of the biggest globular clusters in the Large Magellanic ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.